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Date:      Wed, 04 Apr 2012 08:08:56 +1000
From:      Darren Reed <darrenr@freebsd.org>
To:        Andre Oppermann <andre@freebsd.org>
Cc:        freebsd-net@freebsd.org
Subject:   Re: FreeBSD TCP ignores zero window size
Message-ID:  <4F7B74F8.9080600@freebsd.org>
In-Reply-To: <4F7B3098.3090901@freebsd.org>
References:  <4F75C1A3.4030401@freebsd.org> <4F75D9ED.7080707@freebsd.org> <4F780373.6030107@freebsd.org> <4F7AFEEF.60708@freebsd.org> <4F7B1981.1050009@freebsd.org> <4F7B3098.3090901@freebsd.org>

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On 4/04/2012 3:17 AM, Andre Oppermann wrote:
> On 03.04.2012 17:38, Darren Reed wrote:
>> On 3/04/2012 11:45 PM, Andre Oppermann wrote:
>>> It's the other way around.  remote.ssh is sending old data
>>> which freebsd82.62922 has already ack'ed.  The sessions seems
>>> to be de-synchronized, perhaps some middle box mucking with
>>> the segments trying to modulate something?
>>
>> I suspect that the ISP is dropping packets and/or applying
>> some other means of throttling the connection. So, yes.
> 
> That doesn't explain it.  The other side is retransmitting data
> we have already received and acknowledged!  There is not
> nothing we can do on our side.  That behavior is totally
> non-compliant.
> 
> The zero-window is not involved in this as it would affect
> FreeBSD sending data, not the other end sending data.
> 
> Can you try to find out what kind of middle-box is mucking
> TCP here on your side and the other side?  It must be some
> device that actively touches the TCP session transiting
> through it.  A router with active queue management (like WFQ
> or RED) is not enough to cause this behavior.
> 
> What is the OS of your remote.ssh?

NetBSD.

So its TCP behaviour is going to be a lot like FreeBSD's.

Darren



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